Gas spring assembly for a passenger seat control

ABSTRACT

A gas spring mechanism for adjusting and locking the inclination of one element with respect to another, such as the backrest on a passenger seat. The gas spring has a low melting point plug which melts in the event of a fire to discharge compressed gas in the gas spring and thereby allow for the expansion of working liquid in the gas spring. In one preferred embodiment, the compressed gas contains a fire retardant such as Halon 1301.

This is a division of application Ser. No. 157,893, filed Feb. 19, 1988,now U.S. Pat. No. 4,856,762, issued on Aug. 15, 1989.

BACKGROUND OF THE INVENTION

This invention generally relates to an apparatus for adjusting andlocking the angular position of one member with respect to another whichis especially applicable to the adjustment in inclination of thebackrest of a seat, for example, an aircraft or railway seat, and thelocking thereof by means of a piston cylinder unit. The piston cylinderunit is actuated by an operating cable controlled by push button mountedin the armrest of the seat.

Existing adjustable backrests for seats used in aircraft usuallyincorporate an hydraulic piston cylinder unit in conjunction withmechanical springs for adjusting the inclination of the backrest and thelocking thereof in a desired position. The springs are provided torestore the backrest to its starting position when it is unloaded. Thepush button is mounted on the armrest and, when activated, releases thepiston cylinder unit and the piston rod therein is displaced by theforce of the springs acting on the unit. When the push button isreleased, the piston cylinder unit locks any further movement of thebackrest. In this manner a seat back can be adjusted and locked asdesired within a predetermined angular range.

The hydraulic piston cylinder unit together with the spring system iscomplicated and time consuming to install. However, these hydraulicpiston cylinder units have been used almost exclusively in aircraftseating. One of the important advantages of these prior units was thatlittle force was necessary to operate the push button and this allowedchildren and the physically impaired to actuate the device.

It is recently been found that in fires, the hydraulic piston cylinderunit tends to leak hydraulic fluid which is inflammable and which canadd to the severity of the fire.

What has been needed and heretofore unavailable is a relatively simplepiston cylinder unit which is easy to install and which will not leakhydraulic fluid at elevated temperatures. The present inventionsatisfies this need.

SUMMARY OF THE INVENTION

This invention relates to an apparatus for adjusting the angle of onemember with respect to another such as the back of a passenger seatwhich is pivotally mounted to the horizontal seat portion and to animproved gas spring which is particularly suitable for such use.

The apparatus in accordance with the invention generally includes aremote push button actuating unit which is positioned within an armrestof a passenger seat. A gas spring is connected at one end thereof to thepivotally mounted back portion of the seat and the free end of a pistonrod extending out of the other end of the gas spring is connected to theframe of the horizontal seat portion. A lever actuated assembly, whichis fixed to the frame of the seat moves an actuating member provided onthe free end of the piston rod extending out of the gas spring unit. Theremote actuating unit is operatively connected to the lever actuatingassembly by means of an operating cable, such as a Bowden cable.

The gas spring is provided with an elongated housing having first andsecond pistons slidably disposed within an elongated working chambertherein and separating the working chamber into three subchambers, anintermediate chamber between the first and second pistons, a first endchamber adjacent the side of the first piston opposite the side adjacentthe intermediate chamber and a second end chamber adjacent the side ofthe second piston opposite the side adjacent the intermediate chamber.The first end chamber and the intermediate chamber are filled withincompressible liquid, such as hydraulic fluid, whereas the second endchamber is filled with a compressed, non-combustible gas such asnitrogen, helium, argon, neon, or mixtures thereof. A valve means isprovided to control the flow of incompressible liquid between theintermediate chamber and the first end chamber to facilitate themovement of the first piston therein. The piston rod is secured at oneend to the first piston so that movement of the piston effects movementof the piston rod connected thereto and as a result the inclination ofthe backrest.

In accordance with a preferred embodiment, a conduit is provided betweenthe second end chamber and the exterior of the gas spring which has alow melting point plug. This plug at ambient temperatures prevents theescape of compressed gas once the second end chamber is charged, but inthe event of elevated temperatures, such as found in a fire, the plugwill melt unblocking the conduit and thereby permitting compressed gaswithin the second end chamber to escape to the atmosphere. This escaperelieves pressure within the working chamber of the gas spring givingmore space within the working chamber for hydraulic fluid to expandwithout pressure build up and thereby preventing the escape ofinflammable hydraulic fluid.

In a presently preferred embodiment, the compressed gas has incorporatedtherein a flame retardant such as brominated and fluorinated lowmolecular weight hydrocarbons. The most effective isbromotrifluoromethane which is sold under the trademark Halon 1301 bythe DuPont Company. The brominated, fluorinated hydrocarbons interferewith the combustion process and the interfering reaction thereof issufficiently rapid to prevent combustion and flame propagation even atconcentrations as low as 2% by volume. The brominated, fluorinatedcompounds are relatively non-toxic to humans so that in the event of afire, the escaping gas containing the flame retardant will provide ameasure of protection to a passenger sitting in the seat yet thepassenger is able to breath the gas with no detrimental effects.

In another preferred embodiment, the hydraulic fluid in the first endchamber is replaced with a working fluid containing the brominated,fluorinated hydrocarbons. However, these components are gases at ambientconditions, and they must be maintained under substantial pressure(e.g., 15-30 bars) in order to stay in the liquid phase. Preferably,substantially all of the working fluid is a brominated, fluorinatedhydrocarbon, such as bromotrifluoromethane and dibromodifluoromethane ormixtures thereof. For optimum safety, all three of the separate chambersshould contain the brominated, fluorinated hydrocarbons.

Additionally, an improved method of mounting the control assembly of thegas spring to the frame of the seat is provided. A mounting member fixedto the frame is provided with an opening adapted to receive the free endof the piston rod. A slotted receptacle is provided in the mountingmember which is oriented perpendicularly to the axis of the opening andwhich is adapted to receive a spring clip. The piston rod is providedwith a circumferential groove, and a spring clip is urged into theslotted receptacle to be mounted about the circumferential groove in thefree end of the piston rod in order to fix the free end of the pistonrod to the mounting member secured to the seat frame. Stopping elementsmay be provided on the piston rod to control the maximum movement of thepiston within the cylindrical housing of the gas spring.

The apparatus of the present invention provides an additional measure ofsafety and moreover it can be easily installed and dismantled withsimple tools by personnel with very little mechanical skills. These andother advantages of the invention will become more apparent from thefollowing detailed description thereof when taken in conjunction withthe accompanying exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view with parts exposed of a passenger seat embodyingfeatures of the invention;

FIG. 2 is a cross-sectional view of a gas spring and lever actuatingassembly shown in FIG. 1;

FIG. 3 is a cross-sectional view of a remote actuating unit taken alongthe lines of 3--3 shown in FIG. 1; along

FIG. 4 is a cross-sectional view taken the lines of 4--4 of the remoteactuating unit shown in FIG. 3; and

FIG. 5 is a perspective view of the connection between the operatingcable, a lever actuating assembly, and the gas spring shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Reference is made to FIG. 1 which illustrates a passenger seat 10embodying features of the invention. The seat 10 comprises a horizontalportion 11 supported by an underlying frame 12 shown partially inphantom and a back portion 13 which is pivotally connected to underlyingframe 12. Armrests 14 are provided on each side of the backrest 13.

The system for adjusting and locking the position or inclination of theback portion 13 generally comprises a remote actuating unit 15positioned within the armrest 14, a gas spring 16, and a lever actuatingassembly 17 located in the horizontal seat portion 11, and an operatingcable assembly 18 connected between the remote actuating unit 15 and thelever actuating assembly 17.

The gas spring 16 is secured on one end thereof to the extension element20 on the pivotally mounted back portion 18 by means of a forked headfixture 21. A piston rod 22 extends out of the other end of the gasspring 16 and the end extending out of the housing 23 is releasablyconnected to the mounting member 24 of the lever actuating assembly 17.

Inward movement of the push button 25 of the remote actuating unit 15pulls cable element 26 in the operating cable 18 which in turn causesthe lever 27 on the lever actuating assembly 17 to be pulled toward theend of the piston rod 22 so the button 28 engages the valve release rod30 slidably mounted within the piston rod 22. Inward pressure on therelease rod 30 releases a valve body 31 (shown in FIG. 2) within the gasspring 16 which allows movement of the piston rod 22 inwardly andoutwardly of the gas spring housing 23. If a force is applied to thebackrest 13, as indicated by arrow 32, with the valve body 31 in therelease position, the gas spring housing 23 will be urged toward thelever actuating assembly 17 thereby allowing the backrest 13 to moveinto an inclined position shown in phantom in FIG. 1. If there is noforce applied to the backrest 13, the pressure within the gas spring 16will urge the gas spring housing 23 away from the lever actuatingassembly 17 and result in the backrest 13 moving to an upright position.Removing the pressure from the push button 25 in the remote actuatingunit 15 disengages the valve release rod 30 to lock the gas spring 16and thus locks the backrest 13 in its position at the time of thedisengagement.

The remote actuating unit 15, shown in detail in FIGS. 3 and 4,generally comprises a push button 25 which is slidably mounted within acylindrical bore 33 of housing 34 secured to side panel 35 of thearmrest 14 by means of a threaded or bayonet type collar 36. Acompressed spring 37 is provided to apply tension between the housing 34and the connected collar 36 to maintain the proper position thereofwithin the side panel 35. A two-arm crank 40 is pivotally mounted by pin41 in the housing 34. One arm 42 of the crank 40 is urged against theback side of the push button 25 and the other arm 43 is adapted toreleasably receive an end of the cable element 26 in operating cable 18.The cable element 26 has a small cylindrical body 44 on the end thereofadapted to be seated within a concave recess 45 provided in the far sideof crank arm 43. The arm 43 has a slot (not shown) in the side thereofto the recess 45 so that the cable element 26 can be insertedtherethrough to place the cylindrical body 44 within the concave recess45. The end of covering 47 of the operating Bowden cable 18 is providedwithin fitting 48 which passes through an opening in the housing 34 anda circumferential groove (not shown) is provided in the periphery of thefitting in order to receive a spring clip 50 which secures the end ofthe operating cable 18 in proper position within the housing 34 andprevents the removal therefrom.

The lever actuating assembly 17, best shown in FIGS. 2 and 5, generallycomprises a mounting member 24 which is secured to the frame 12 (shownpartially in phantom) supporting the horizontal seat portion 11. Leverarm 27 is pivotally mounted about pin 51 at one end thereof to ears 52and 53 of the mounting member 24. The free end of lever arm 27 isadapted to receive the end of the cable element 26 in a manner similarto the cable connection in remote actuating unit 15. A cylindrical body54 is provided on the end of the cable element 26 which is adapted to beseated within the concave recess 55 provided in the opposite face of thelever arm 27. A slotted opening (not shown) is provided in the side ofthe free end of lever arm 27 to the recess 55 to allow the cable element26 to be inserted in order to place the cylindrical body 54 into theconcave recess 55. A fitting 56 within a groove 57 in the peripherythereof passes through opening 58 and a spring clip 59 engages thegroove 57 to hold the fitting. A threaded collar 60 is provided to betightened against the mounting member 24 in the side opposite the springclip 59 to fix the end of the cable 18 to the mounting member 24 and toadjust the length of the cable so that button 28 has direct contact withrelease rod 30.

The free end of piston rod 22 which extends out of the gas springhousing 23 is seated within opening 61 provided in mounting member 24and a spring clip 62 is inserted through the slotted opening 63 of thereceiving receptacle 64, as shown best in FIG. 5, and engages a groove66 in the periphery of the piston rod 22 to thereby fix the free endwithin the receptacle 64. A valve release rod 30 slidably mounted in anaxial bore within the piston rod 22 extends out of the free end of thepiston rod 22 and is engaged by pressing element or button 28 on theinside of the lever arm 27 when the lever arm is pulled by cable element26. This pushes the valve release rod 30 into piston rod 22 to activatea valve body 31 within the gas spring housing 23, shown in FIG. 2.

The details of the gas spring 16 embodying features of the invention arebest illustrated in FIG. 2. As shown therein, the gas spring 16generally comprises a cylindrical housing or outer shell 23 and an innerworking chamber 67 disposed therein. A first piston 68 and a secondpiston 69 are slidably and sealingly mounted within the working chamber67 and divide the working chamber into three separate chambers, anintermediate chamber 70 between the first and second piston 68 and 69, afirst end chamber 71 disposed on the side 72 of the first piston 68opposite the intermediate chamber 70, and a second end chamber 73disposed on the side 74 of the second piston 69 opposite theintermediate chamber 70. The inner end 75 of valve release rod 30 isslidably disposed within the axial bore of piston rod 22 and engages thetapered end 76 of the valve body 31 so that when the valve releasing rod30 is pushed inwardly toward the valve body 31, it is lifted out of thevalve seat provided, allowing hydraulic fluid within the working chamber67 to pass through a central opening 77 in the valve seat and conduit 78in the first piston 68 and to thereby flow between the intermediatechamber 70 and the first end chamber 71. Lifting the valve body 31 andallowing hydraulic fluid to flow therethrough forces the first piston 68to move within the working chamber 67, and, as a result, the piston rod22 attached thereto. Release of the valve release rod 30 resets valvebody 31 into the valve seat to thereby lock the position of the firstpiston and the attached piston rod.

The second end chamber 73 is charged with compresed gas urging thesecond piston 69 toward the first piston 68 thereby maintaining thehydraulic fluid contained in the intermedite chamber 70 under pressure.The pressure of the compressed gas acting against the second piston 69is chosen so that when the push button 25 of the remote actuating unit15 is pushed, thereby lifting the valve body 31 from the valve seat andif no force is applied to the backrest 13 in the direction of the arrow32 shown in FIG. 1, enough force will be generated on the piston rod 22to pivot the backrest 13 to its upright position, shown in FIG. 1.

A guiding element 80 is provided within the gas spring housing 23 toengage the exterior of the piston rod 22 and guide the axial movementthereof within the housing. O-ring gaskets 81 and 82 are provided toprevent the escape of hydraulic fluid therethrough and a grease chamber83 is positioned about the periphery of rod 22 to provide lubrication.

In accordance with a very important aspect of the invention, theopposite end 84 of the housing 23 is provided with a closing member 85which has an interior passageway or conduit 86 which is blocked off witha plug 87 formed from a low melting point alloy which will melt at theelevated temperatures which the gas spring 16 might be exposed to in afire situation. When the plug 87 melts, the compressed gas in the secondend chamber escapes through the conduit 86 and thereby relieves thepressure within the working chamber 67. This allows the incompressibleliquid within the working chamber 67 to expand and prevents the lossthereof from the gas spring 16. The low melting point plug 87 providedin the conduit 86 generally may be formed from a low melting point alloysuch as alloys of tin, lead, cadmium, zinc and mixtures thereof. Typicalmelting points range from about 80° to 350° C.

The compressed gas within the second end chamber 73 should be anon-combustible gas such as nitrogen, helium, argon, and neon ormixtures thereof. Pressures of the compressed gas may range from about40 to 60 bars. Preferably, a fire retardant is incorporated into thecompressed gas which sufficiently interferes with the combustion processto retard combustion in the area surrounding the seat upon the escapethereof from the gas spring. The preferred fire retardant isbromotrifluoromethane which is essentially non-toxic to humans even inconcentrations as high as 10% by volume and are very effective inpreventing combustion and flame propagation. These fire retardants aresold under the trademark Halon 1301 by the DuPont Company. Under thenormal pressures of the compressed gas, the brominated, fluorinatedhydrocarbons may exist at least in part in the liquid state. In theevent of a fire, the plug 87 will melt, the compressed gas will escapethe gas spring and envelope a passenger sitting in the seat. The fireretardant, because of the lowered pressure, will very rapidly vaporize,thus preventing combustion in this vicinity. However, the surroundinggas will not have any detrimental effects on the passenger. If desired,additional conduits can be provided in fluid communication with conduit86 to direct gas escaping from the second end chamber 73 around apassenger sitting in the seat.

If the hydraulic fluid in the intermediate chamber 70 and first endchamber 71 is replaced by a fluid containing brominated, fluorinatedhydrocarbons, a conduit, such as conduit 86 is provided between theintermediate chamber 70 or first end chamber 71 (or both) with a lowmelting point plug therein, such as plug 87, to exhaust the fireretardant gases when the temperature exceeds a predetermined maximum. Ifall or a substantial portion of the seating in an aircraft is providedwith the gas spring in accordance with this invention, sufficient fireretardant can escape into the interior of the aircraft in the event of afire to preclude further combustion.

While the invention has been described herein in connection with apassenger seat, it can be used in a wide variety of situations where thepositional movement of one body with respect to another is controlled byan hydraulic cylinder. For example, the gas spring could be used in theoverhead compartments in aircraft, trunk lids in automobiles, and manyother uses. These and other modifications and improvements can be madewithout departing from the scope thereof.

What is claimed is:
 1. An apparatus for adjusting and locking theposition of one member with respect to another member comprising:(a) agas spring assembly having an elongated housing one end of which issecured to one of said members and a piston rod extending out of theother end of the housing having a valve release rod thereon and beingsecured to the said other member; (b) a remote actuating assembly havinga push button, a pivotally mounted two-arm crank, one of said armsoperatively engaging a back side of the push button and the other armreceiving one end of an operating cable; and (c) a lever actuatingassembly mounted to a support frame for one of said members including amounting element, a lever arm pivotally mounted at one end thereof tothe mounting element and having the other end of the operating cableremovably secured to the free end of the lever arm, means on the leverarm to engage the valve release rod on the end of the piston rod, themounting element having a first opening to receive the free end of thepiston rod, a slotted receptacle adjacent and perpendicular to the firstopening and adapted to receive a first spring clip, the first springclip sliding through the receptacle to be mounted about acircumferential groove provided in the free end of the piston rod tothereby retain the free end of the piston rod in position so thatmovement of the operating cable caused by pressing on the push button ofthe remote actuator assembly will cause the lever arm to pivot and themeans thereon to engage the valve release rod to open a valve and allowmovement of hydraulic fluid between a first end chamber and anintermediate chamber.
 2. The apparatus of claim 10 wherein the ends ofthe operating cable has provided thereon fittings which have acircumferential groove therein.
 3. The apparatus of claim 11 wherein theremote actuating assembly is provided with a housing to leave an openingtherein adapted to receive the fitting on one of the ends of theoperating cable and a second spring clip engages the circumferentialgroove.
 4. The apparatus of claim 12 wherein the mounting element of thelever actuating assembly is provided with an opening therein adapted toreceive the fitting on the other end of the operating cable and a thirdspring clip engages the circumferential groove.
 5. The apparatus ofclaim 1 wherein at least one of the ends of the operating cable isprovided with a threaded collar adapted to urge against the surface onsaid mounting element opposite the side adjacent the spring clipengaging that end of the operating cable.
 6. The apparatus of claim 1wherein the operating cable comprises an outer covering and a cableelement slidably positioned within the cable covering.